The distribution and fractionation of beryllium isotopes in various reactive phases of Antarctic marine sediments

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dc.contributor.authorJeromson, MRen_AU
dc.contributor.authorFujioka, Ten_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorPost, Aen_AU
dc.contributor.authorSimon, KJen_AU
dc.contributor.authorSánchez-Palacios, JTen_AU
dc.contributor.authorBlaxell, Men_AU
dc.contributor.authorEnge, TGen_AU
dc.contributor.authorWilcken, KMen_AU
dc.contributor.authorWhite, DAen_AU
dc.date.accessioned2023-01-19T23:05:03Zen_AU
dc.date.available2023-01-19T23:05:03Zen_AU
dc.date.issued2021-11en_AU
dc.date.statistics2022-06-03en_AU
dc.description.abstractBeryllium isotopes, ¹⁰ Be and ⁹ Be, in Antarctic marine sediments are increasingly being applied as paleoenvironmental proxies and indicators of past ice shelf extent. The evidence base for interpreting meteoric-¹⁰ Be concentrations and ¹⁰ Be/⁹ Be ratios has largely been derived from examining their spatial distribution in modern depositional environments, or by correlation with other proxies in paleo-records, such as diatom abundance. Meteoric-¹⁰ Be is geochemically adsorbed onto sediment grains in the reactive phase during transport from the atmosphere to deposition on the seafloor. Unlike meteoric-¹⁰ Be, ⁹ Be is both available within the reactive phase after crustal weathering and native within mineral lattice in significant quantities. The complexity in fixing and preserving the Be isotopes onto grain surfaces leads to uncertainties in selecting the chemistry methods to consistently extract the reactive phases of ¹⁰ Be and ⁹ Be in different sediments. This gap in understanding the physical behaviour and geochemical forms of reactive Be in Antarctic sediments limits their utility in reconstruction of paleoenvironmental conditions. We conducted a sequential leach procedure on three homogenised sediment grab samples from the front of the Amery Ice Shelf that span a range of water masses. Using different chemical reagents, from very weak to very strong, five phases of Be isotope signatures were extracted sequentially, including : i) water soluble, ii) amorphous oxides leached by 0.5M HCl, iii) crystalline oxides leached by 1M NH₂ OH-HCl in 1M HCl, iv) organic leached by 0.01M HNO₃ and H₂ O₂ , and v) mineral/residual phase dissolved by HF– with the water through to organic leach making the reactive phase. We found that the amorphous and crystalline oxide phases contained the largest fraction of ¹⁰ Be, about 90% of total ¹⁰ Be, with the remaining 10% being in the mineral/residual phase. For ⁹ Be, the oxide phases contained only 10-30%, the majority of ⁹ Be being in the residual phase. The water-soluble and organic chemical treatments were inefficient in extracting any significant reactive Be. This distribution has been observed in other deep marine and continental riverine sediments. However, the proportional distribution of the two isotopes between the amorphous and crystalline oxides differed for our Antarctic sediments compared to those other studies. While reactive ⁹ Be was close to equally split across the two oxide phases, 80% of reactive ¹⁰ Be was located within the amorphous phase, with the remainder within the crystalline oxide phase. The difference in fractionation provides evidence for different sources of each isotope and different processes affecting their deposition. ⁹ Be is sourced primarily from the Earth’s crust and is likely segregated into the different fractions during the process of subglacial chemical weathering. Open water ¹⁰ Be is processed in the water column, where interaction with biogeochemical processes likely segregates it into the more labile phases. These findings inform decisions regarding the selection of procedures for efficient and reproducible extraction of meteoric-¹⁰ Be, and for understanding the processes that drive the source and distribution of different isotopes around ice shelf systems. © The Authorsen_AU
dc.identifier.citationJeromson, M., Fujioka, T., Fink, D., Post, A., Simon, K., Sanchez-Palacios, J. T., Blaxell, M., Enge, T. G., Wilcken, K., & White, D. (2021). The distribution and fractionation of beryllium isotopes in various reactive phases of Antarctic marine sediments. Paper presented to the 15th International Conference on Accelerator Mass Spectrometry. ANSTO Sydney, Australia. November 15th – 19th, 2021, (pp. 86). Retrieved from: https://ams15sydney.com/wp-content/uploads/2021/11/AMS-15-Full-Program-and-Abstract-Book-R-1.pdfen_AU
dc.identifier.conferenceenddate19 November 2021en_AU
dc.identifier.conferencename15th International Conference on Accelerator Mass Spectrometryen_AU
dc.identifier.conferenceplaceSydney, Australiaen_AU
dc.identifier.conferencestartdate15 November 2021en_AU
dc.identifier.pagination86en_AU
dc.identifier.urihttps://ams15sydney.com/wp-content/uploads/2021/11/AMS-15-Full-Program-and-Abstract-Book-R-1.pdfen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14430en_AU
dc.language.isoenen_AU
dc.publisherAustralian Nuclear Science and Technology Organisationen_AU
dc.subjectBerylliumen_AU
dc.subjectIsotopesen_AU
dc.subjectAntarcticaen_AU
dc.subjectSedimentsen_AU
dc.subjectBeryllium 10en_AU
dc.subjectAquatic ecosystemsen_AU
dc.subjectIceen_AU
dc.subjectDiatomsen_AU
dc.subjectWater chemistryen_AU
dc.titleThe distribution and fractionation of beryllium isotopes in various reactive phases of Antarctic marine sedimentsen_AU
dc.typeConference Abstracten_AU
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